Editing Advanced Audio Coding (section)

==History==
===Background===
The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing their results in 1974.<ref name="Ahmed">{{cite journal |last=Ahmed |first=Nasir |author-link=N. Ahmed |title=How I Came Up With the Discrete Cosine Transform |journal=[[Digital Signal Processing (journal)|Digital Signal Processing]] |date=January 1991 |volume=1 |issue=1 |pages=4–5 |doi=10.1016/1051-2004(91)90086-Z |bibcode=1991DSP.....1....4A |url=https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform|url-access=subscription }}</ref><ref name="pubDCT">{{Citation |first1=Nasir |last1=Ahmed |author1-link=N. Ahmed |first2=T. |last2=Natarajan |first3=K. R. |last3=Rao |title=Discrete Cosine Transform |journal=IEEE Transactions on Computers |date=January 1974 |volume=C-23 |issue=1 |pages=90–93 |doi=10.1109/T-C.1974.223784|s2cid=149806273 }}</ref><ref name="pubRaoYip">{{Citation |last1=Rao |first1=K. R. |author-link1=K. R. Rao |last2=Yip |first2=P. |title=Discrete Cosine Transform: Algorithms, Advantages, Applications |publisher=Academic Press |location=Boston |year=1990 |isbn=978-0-12-580203-1}}</ref> This led to the development of the [[modified discrete cosine transform]] (MDCT), proposed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987,<ref>J. P. Princen, A. W. Johnson und A. B. Bradley: ''Subband/transform coding using filter bank designs based on time domain aliasing cancellation'', IEEE Proc. Intl. Conference on Acoustics, Speech, and Signal Processing (ICASSP), 2161–2164, 1987</ref> following earlier work by Princen and Bradley in 1986.<ref>John P. Princen, Alan B. Bradley: ''Analysis/synthesis filter bank design based on time domain aliasing cancellation'', IEEE Trans. Acoust. Speech Signal Processing, ''ASSP-34'' (5), 1153–1161, 1986</ref> The [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<ref name="Guckert">{{cite web |last1=Guckert |first1=John |title=The Use of FFT and MDCT in MP3 Audio Compression |url=http://www.math.utah.edu/~gustafso/s2012/2270/web-projects/Guckert-audio-compression-svd-mdct-MP3.pdf |website=[[University of Utah]] |date=Spring 2012 |access-date=14 July 2019}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web |last=Borland |first=John |date=March 18, 2004 |title=The sound of science |url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ |access-date=2023-04-21 |website=CNET |language=en}}</ref>

AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society|Fraunhofer IIS]] (who developed MP3) and [[Sony|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report |url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf |title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio |date=1 September 2009 |access-date=2009-10-07 |archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf |url-status=live |archive-date=14 June 2011 |publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone|NTT]].<ref name="aac-licensors">{{cite web |title=AAC Licensors |url=https://www.via-corp.com/licensing/aac/aac-licensors/ |access-date=15 January 2020 |website=Via Corp}}</ref><ref name="businesswire">{{cite web |date=5 January 2009 |title=Via Licensing Announces Updated AAC Joint Patent License |url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License |access-date=18 June 2019 |website=[[Business Wire]]}}</ref>

===Standardization===
{{Confusing section|date=April 2025}}
In 1997, AAC was first introduced as ''MPEG-2 Part 7'', formally known as ''[[ISO]]/[[IEC]] 13818-7:1997''. This part of MPEG-2 was a new part, since MPEG-2 already included ''MPEG-2 Part 3'', formally known as ''ISO/IEC 13818-3: MPEG-2 BC'' (Backwards Compatible).<ref name="mpeg-bc">{{cite web | url=http://www.mpeg.org/MPEG/audio/aac.html | title=AAC | website=MPEG.ORG | access-date=2009-10-28 | archive-url=https://web.archive.org/web/20091003042614/http://www.mpeg.org/MPEG/audio/aac.html | archive-date=3 October 2009 | url-status=dead }}</ref><ref name="iso13818-7-2006-pdf">{{cite web | url=http://webstore.iec.ch/preview/info_isoiec13818-7%7Bed4.0%7Den.pdf | title=ISO/IEC 13818-7, Fourth edition, Part 7 - Advanced Audio Coding (AAC) | publisher=[[ISO]] | date=15 January 2006 | access-date=2009-10-28 | url-status=live | archive-url=https://web.archive.org/web/20090306055335/http://webstore.iec.ch/preview/info_isoiec13818-7%7Bed4.0%7Den.pdf | archive-date=6 March 2009 }}</ref> Therefore, MPEG-2 Part 7 is also known as ''MPEG-2 NBC'' (Non-Backward Compatible), because it is not compatible with the [[MPEG-1]] audio formats ([[MP1]], [[MPEG-1 Audio Layer II|MP2]] and [[MP3]]).<ref name="mpeg-bc" /><ref>{{cite web | url=http://www.mp3-tech.org/aac.html | title=MPEG-2/MPEG-4 - AAC | year=2003 | first=Gabriel | last=Bouvigne | publisher=MP3'Tech | access-date=2009-10-28 | url-status=live | archive-url=https://web.archive.org/web/20100105022907/http://www.mp3-tech.org/aac.html | archive-date=2010-01-05 }}</ref><ref name="mpeg-audio-faq-bc">{{cite web | url=http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm | title=MPEG Audio FAQ Version 9 - MPEG-1 and MPEG-2 BC | publisher=[[ISO]] | date=October 1998 | access-date=2009-10-28 | url-status=live | archive-url=https://web.archive.org/web/20100218081343/http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm | archive-date=2010-02-18 }}</ref><ref name="mpeg-audio-florence">{{cite web|url=http://mpeg.chiariglione.org/meetings/firenze/prfloren.htm |title=Florence Press Release |publisher=[[ISO]] |date=March 1996 |access-date=2009-10-28 |url-status=dead |archive-url=https://web.archive.org/web/20100408061828/http://mpeg.chiariglione.org/meetings/firenze/prfloren.htm |archive-date=2010-04-08 }}</ref>

MPEG-2 Part 7 defined three profiles: ''Low-Complexity'' profile (AAC-LC / LC-AAC), ''Main'' profile (AAC Main) and ''Scalable Sampling Rate'' profile (AAC-SSR). AAC-LC profile consists of a base format very much like AT&T's Perceptual Audio Coding (PAC) coding format,<ref>Johnston, J. D. and Ferreira, A. J., "Sum-difference stereo transform coding", ICASSP '92, March 1992, pp. II-569-572.</ref><ref>Sinha, D. and Johnston, J. D., "Audio compression at low bit rates using a signal adaptive switched filterbank", IEEE ASSP, 1996, pp. 1053-1057.</ref><ref>Johnston, J. D., Sinha, D., Dorward, S. and Quackenbush, S., "AT&T perceptual audio coder (PAC)" in Collected Papers on Digital Audio Bit-Rate Reduction, Gilchrist, N. and Grewin, C. (Ed.), Audio Engineering Society, 1996.</ref> with the addition of [[temporal noise shaping]] (TNS),<ref>Herre, J. and Johnston, J. D., "Enhancing the performance of perceptual audio coders by using temporal noise shaping", AES 101st Convention, no. preprint 4384, 1996</ref> the [[Kaiser window]] (described below), a nonuniform [[quantizer]], and a reworking of the bitstream format to handle up to 16 stereo channels, 16 mono channels, 16 low-frequency effect (LFE) channels and 16 commentary channels in one bitstream. The Main profile adds a set of recursive predictors that are calculated on each tap of the filterbank. The [[Scalable Samping Rate Profile|SSR]] uses a 4-band [[Pseudo Quadrature Mirror Filter|PQMF]] filterbank, with four shorter filterbanks following, in order to allow for scalable sampling rates.

In 1999, MPEG-2 Part 7 was updated and included in the MPEG-4 family of standards and became known as ''[[MPEG-4 Part 3]]'', ''MPEG-4 Audio'' or ''ISO/IEC 14496-3:1999''. This update included several improvements. One of these improvements was the addition of ''[[MPEG-4 Part 3#MPEG-4 Audio Object Types|Audio Object Types]]'' which are used to allow interoperability with a diverse range of other audio formats such as [[TwinVQ]], [[CELP]], [[HVXC]], [[speech synthesis]] and [[MPEG-4 Structured Audio]]. Another notable addition in this version of the AAC standard is ''Perceptual Noise Substitution'' (PNS). In that regard, the AAC profiles (AAC-LC, AAC Main and AAC-SSR profiles) are combined with perceptual noise substitution and are defined in the MPEG-4 audio standard as Audio Object Types.<ref name="mpeg4audio-profiles">{{cite web|url=http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/profiles.html |title=MPEG-4 Natural Audio Coding - Audio profiles and levels |first1=Karlheinz |last1=Brandenburg |first2=Oliver |last2=Kunz |first3=Akihiko |last3=Sugiyama |website=chiariglione.org |access-date=2009-10-06 |url-status=dead |archive-url=https://web.archive.org/web/20100717130019/http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/profiles.html |archive-date=2010-07-17 }}</ref> MPEG-4 Audio Object Types are combined in four MPEG-4 Audio profiles: Main (which includes most of the MPEG-4 Audio Object Types), Scalable (AAC LC, AAC LTP, CELP, HVXC, TwinVQ, Wavetable Synthesis, TTSI), Speech (CELP, HVXC, TTSI) and Low Rate Synthesis (Wavetable Synthesis, TTSI).<ref name="mpeg4audio-profiles" /><ref name="mpeg4audio-version1-draft">{{cite web | url=https://www.itscj.ipsj.or.jp/sc29/open/29view/29n2603t0.pdf | title=ISO/IEC FCD 14496-3 Subpart 1 - Draft - N2203 | publisher=[[ISO]]/[[IEC]] JTC 1/SC 29/WG 11 | date=15 May 1998 | access-date=2009-10-07 }}</ref>

The reference software for MPEG-4 Part 3 is specified in MPEG-4 Part 5 and the conformance bit-streams are specified in MPEG-4 Part 4. MPEG-4 Audio remains [[backward-compatible]] with MPEG-2 Part 7.<ref name="mpeg4audio-mpeg2audio">{{cite web|url=http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html |title=MPEG-4 Natural Audio Coding - General Audio Coding (AAC based) |first1=Karlheinz |last1=Brandenburg |first2=Oliver |last2=Kunz |first3=Akihiko |last3=Sugiyama |website=chiariglione.org |year=1999 |access-date=2009-10-06 |url-status=dead |archive-url=https://web.archive.org/web/20100219233137/http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html |archive-date=2010-02-19 }}</ref>

The MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000) defined new audio object types: the low delay AAC ([[AAC-LD]]) object type, bit-sliced arithmetic coding (BSAC) object type, parametric audio coding using [[Harmonic and Individual Lines and Noise|harmonic and individual line plus noise]] and error resilient (ER) versions of object types.<ref name="mpeg4audio-iso-2-amd">{{cite web | url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 | title=ISO/IEC 14496-3:1999/Amd 1:2000 - Audio extensions | publisher=[[ISO]] | year=2000 | access-date=2009-10-07 | url-status=live | archive-url=https://web.archive.org/web/20110606215234/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 | archive-date=2011-06-06 }}</ref><ref name="mpeg4audio-version2">{{Cite FTP | url=ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf | title=ISO/IEC 14496-3:/Amd.1 - Final Committee Draft - MPEG-4 Audio Version 2 | date=July 1999 | access-date=2009-10-07 | url-status=dead | server=[[ISO]]/[[IEC]] JTC 1/SC 29/WG 11 }}</ref><ref name="mpeg4audio2">{{cite web|url=https://sound.media.mit.edu/resources/mpeg4/audio/general/aes108_6-Parametric.pdf|title=MPEG-4 Version 2 Audio Workshop:HILN - Parametric Audio Coding|at=AES 108th Convention: MPEG-4 Version 2 Audio What is it about?|location=Paris| first1=Heiko |last1=Purnhagen | date=19 February 2000 | access-date=2009-10-07}}</ref> It also defined four new audio profiles: High Quality Audio Profile, Low Delay Audio Profile, Natural Audio Profile and Mobile Audio Internetworking Profile.<ref name="mpeg4-profiles">{{cite web|url=http://www.m4if.org/resources/profiles/audio.php |archive-url=http://webarchive.loc.gov/all/20100108152236/http://www.m4if.org/resources/profiles/audio.php |url-status=dead |archive-date=2010-01-08 |title=Levels for Audio Profiles |first1=Fernando |last1=Pereira |publisher=MPEG Industry Forum |date=October 2001 |access-date=2009-10-15 }}</ref>

The [[HE-AAC]] Profile (AAC LC with [[Spectral band replication|SBR]]) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.<ref name="he-aac-amd1">{{cite web | url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 | title=ISO/IEC 14496-3:2001/Amd 1:2003 - Bandwidth extension | publisher=[[ISO]] | year=2003 | access-date=2009-10-07 | url-status=live | archive-url=https://web.archive.org/web/20110606054451/http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 | archive-date=2011-06-06 }}</ref> The HE-AAC v2 Profile (AAC LC with SBR and Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016">{{cite web|url=http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc |title=Text of ISO/IEC 14496-3:2001/FPDAM 4, Audio Lossless Coding (ALS), new audio profiles and BSAC extensions |format=DOC |publisher=[[ISO]]/[[IEC]] JTC1/SC29/WG11/N7016 |date=11 January 2005 |access-date=2009-10-09 |url-status=dead |archive-url=https://web.archive.org/web/20140512215821/http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc |archive-date=12 May 2014 }}</ref><ref name="ISO 14496-3:2005/Amd.2">{{cite web | title=Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, ISO/IEC 14496-3:2005/Amd 2:2006 | url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 | publisher=[[ISO]] | year=2006 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20120104072435/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 | archive-date=2012-01-04 }}</ref><ref name="embedded">{{cite web | title=Audio compression gets better and more complex | url=http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex | first=Mihir | last=Mody | website=Embedded.com | date=6 June 2005 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20160208004827/http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex | archive-date=8 February 2016 }}</ref> The Parametric Stereo audio object type used in HE-AAC v2 was first defined in ISO/IEC 14496-3:2001/Amd 2:2004.<ref name="CT-whitepaper">{{cite web|url=http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf |title=MPEG-4 aacPlus - Audio coding for today's digital media world|access-date=2007-01-29 |url-status=dead |archive-url=https://web.archive.org/web/20061026031407/http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf |archive-date=2006-10-26 }}</ref><ref name="parametric">{{cite web | title=Parametric coding for high-quality audio, ISO/IEC 14496-3:2001/Amd 2:2004 | url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 | publisher=[[ISO]] | year=2004 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20120104071002/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 | archive-date=2012-01-04 }}</ref><ref name="3gpp26401">{{cite web | title=3GPP TS 26.401 V6.0.0 (2004-09), General Audio Codec audio processing functions; Enhanced aacPlus General Audio Codec; General Description (Release 6) | url=http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip | format=DOC | publisher=3GPP | date=30 September 2004 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20060819083421/http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip | archive-date=19 August 2006 }}</ref>

The current version of the AAC standard is defined in ISO/IEC 14496-3:2009.<ref name="mpeg4audio-2009">{{cite web | url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=53943 | title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio | publisher=[[ISO]] | year=2009 | access-date=2009-10-07 | url-status=live | archive-url=https://web.archive.org/web/20110606214516/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=53943 | archive-date=2011-06-06 }}</ref>

AAC+ v2 is also standardized by [[ETSI]] ([[European Telecommunications Standards Institute]]) as TS 102005.<ref name="CT-whitepaper" />

The [[MPEG-4 Part 3]] standard also contains other ways of compressing sound. These include lossless compression formats, synthetic audio and low bit-rate compression formats generally used for speech.

===AAC's improvements over MP3===
Advanced Audio Coding is designed to be the successor of the ''[[MPEG-1 Audio Layer 3]]'', known as MP3 format, which was specified by [[ISO]]/[[IEC]] in 11172-3 ([[MPEG-1]] Audio) and 13818-3 ([[MPEG-2]] Audio).

Improvements include:
* more [[sample rate]]s (from 8 to 96 [[kHz]]) than MP3 (16 to 48&nbsp;kHz);
* up to 48 channels (MP3 supports up to two channels in MPEG-1 mode and up to [[5.1]] channels in MPEG-2 mode);
* arbitrary [[bit rate]]s and variable frame length. Standardized constant bit rate with bit reservoir;
* higher efficiency and simpler [[filter bank]]. AAC uses a pure [[MDCT]] (modified discrete cosine transform), rather than MP3's hybrid coding (which was part MDCT and part [[FFT]]);
* higher coding efficiency for [[Stationary process|stationary signals]] (AAC uses a blocksize of 1024 or 960 samples, allowing more efficient coding than MP3's 576 sample blocks);
* higher coding accuracy for [[Transient (acoustics)|transient signals]] (AAC uses a blocksize of 128 or 120 samples, allowing more accurate coding than MP3's 192 sample blocks);
* possibility to use [[Kaiser window|Kaiser-Bessel derived]] window function to eliminate [[spectral leakage]] at the expense of widening the main lobe;
* much better handling of audio frequencies above 16&nbsp;kHz;
* more flexible [[joint stereo]] (different methods can be used in different frequency ranges);
* additional modules (tools) added to increase compression efficiency: [[Noise shaping|TNS]], backwards prediction, perceptual noise substitution (PNS), etc. These modules can be combined to constitute different encoding profiles.

Overall, the AAC format allows developers more flexibility to design codecs than MP3 does, and corrects many of the design choices made in the original MPEG-1 audio specification. This increased flexibility often leads to more concurrent encoding strategies and, as a result, to more efficient compression. This is especially true at very low bit rates where the superior stereo coding, pure MDCT, and better transform window sizes leave MP3 unable to compete.

=== Adoption ===
While the MP3 format has near-universal hardware and software support, primarily because MP3 was the format of choice during the crucial first few years of widespread music [[file-sharing]]/distribution over the internet, AAC remained a strong contender due to some unwavering industry support.<ref>{{cite web |title=AAC |url=http://wiki.hydrogenaud.io/index.php?title=AAC |url-status=live |archive-url=https://web.archive.org/web/20140706172307/http://wiki.hydrogenaud.io/index.php?title=AAC |archive-date=2014-07-06 |access-date=2011-01-24 |publisher=Hydrogenaudio}}</ref> Due to MP3's dominance, adoption of AAC was initially slow. The first commercialization was in 1997 when [[AT&T Labs]] (a co-owner of AAC patents) launched a digital music store with songs encoded in MPEG-2 AAC.<ref name=":2">{{Cite web |date=2001-08-08 |title=News: A higher standard for digital music |website=[[ZDNet]] |url=https://www.zdnet.com/zdnn/stories/comment/0,5859,2699666,00.html |access-date=2025-04-11 |archive-url=https://web.archive.org/web/20010808234826/https://www.zdnet.com/zdnn/stories/comment/0,5859,2699666,00.html |archive-date=8 August 2001 }}</ref> HomeBoy for Windows was one of the earliest available AAC encoders and decoders.<ref>{{Cite web |title=ReallyRareWares - HomeBoy AAC encoder |url=https://www.rarewares.org/rrw/homeboy.php |access-date=2025-04-11 |website=www.rarewares.org}}</ref>

[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web |last=RadioWorld |date=2002-03-26 |title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program |url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program |access-date=2025-04-11 |website=Radio World |language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].

Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web |title=Carrying A Tune With Nokia Phones |url=https://www.forbes.com/2001/08/30/0830tentech.html |access-date=2025-04-11 |website=Forbes |language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite magazine |author=WIRED Staff |title=A Music File by Any Other Name |url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ |access-date=2025-04-11 |magazine=Wired |language=en-US |issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite magazine |last=Buskirk |first=Eliot Van |title=In EMI-ITunes Deal, the Big Loser May Be Microsoft |url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ |access-date=2025-04-11 |magazine=Wired |language=en-US |issn=1059-1028}}</ref>

By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web |author1=What Hi-Fi Admin |date=2017-05-15 |title=Home |url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme |access-date=2025-04-11 |website=whathifi |language=en}}</ref>